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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Where is the fuse on the Armstrong Ultra SX 80? 48 hours.

Customer Question

Where is the fuse on the Armstrong Ultra SX 80?
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: 48 hours. Had an Ecobee 3 installed 7 weeks ago with no problem. 2 days ago the AC went off and the Ecobee was reading crazy high room temp reading. Ecobee tech had me rewire it (it was previously installed by a certified electrician) and now it won't work. They told me told check the 5 amp fuse. Can't find it. Is it like a car fuse?
JA: Do you plan on doing the work yourself?
Customer: If it's just a matter of checking/changing a fuse, then yes. I rewired it per the recommendations.
JA: Anything else we should know to help you best?
Customer: The AC unit could be over 20 years old. So the problem could've originated with that. But no power coming from furnace panel, per Ecobee tech. Is there a fuse on that panel?
JA: Did you check the furnace's filters?
Customer: I just changed it yesterday.
Submitted: 9 months ago.
Category: HVAC
Expert:  Tim H. replied 9 months ago.

Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Please provide all information I request as it makes it more difficult to troubleshoot something when I'm not there onsite. Essentially, you become my eyes and ears. Thanks for the opportunity to help. At the end of our dialog, you will have a chance to rate my service, but please wait until we are finished and you're satisfied you have all the information you need. Please be patient as many times we work with several customers at once.

The fuse is exactly like a car fuse and will be on the printed circuit board which is usually located in the blower compartment.

Customer: replied 9 months ago.
Like on a car, just a small plastic fuse with no wires attached. I'm looking right at the board and I don't see it.
Customer: replied 9 months ago.
Expert:  Tim H. replied 9 months ago.

Yup, looking at your pictures.

Expert:  Tim H. replied 9 months ago.

Board is pretty dirty. Look for a fuse similar to this.

Customer: replied 9 months ago.
Is the filter in the right direction, by the way? I didn't put that in (another family member did).
Expert:  Tim H. replied 9 months ago.

Arrow should point towards furnace.

Customer: replied 9 months ago.
Expert:  Tim H. replied 9 months ago.

That looks OK.

Customer: replied 9 months ago.
Can't find the fuse :(
Expert:  Tim H. replied 9 months ago.

Your board may not have one, then. Not all boards have fuses although the majority do.

Customer: replied 9 months ago.
How would I know if it broke then?
Expert:  Tim H. replied 9 months ago.

You would need to take some voltage readings for me.

Customer: replied 9 months ago.
I don't have a voltage reader. Gotta go get one.
Expert:  Tim H. replied 9 months ago.

OK, let me know, please.